WEDNESDAY, Feb. 29 (HealthDay News) -- Patients who have heart disease and take cholesterol-lowering medicines known as statins are less likely to develop depression than those not on such drugs, a new study suggests.

For the study, Dr. Mary Whooley of the San Francisco VA Medical Center and colleagues evaluated 965 heart disease patients for depression. The researchers found those taking statins were less likely to be depressed.

Next, they followed the 776 who were not depressed for another six years. Of those, 520 were taking statins; the others were not.

While 18.5 percent of those on statins developed depression during the follow-up, 28 percent of those not on the medicines developed depression, which translates to a 38 percent reduced risk of developing depression, Whooley said.

The study is published online Feb. 21 in the Journal of Clinical Psychiatry.

While the study found a link between statin use and a reduced risk of depression, it did not prove that the drugs help patients avoid mental health problems.

The message is not to take statins for depression risk, Whooley said, but that a possible benefit of the drugs, when they are needed, is to reduce depression risk. "Statins are great for cholesterol, and do not have any harmful effects on mood, but should not be used to treat depression," she noted.

Statin use is very common. In the United States, about 36 million patients are eligible for statin prescriptions for heart disease prevention, Whooley added.

On Tuesday, the U.S. Food and Drug Administration issued an update on statins, warning consumers that some statin users report memory loss, some have elevated blood sugar levels and other risks.

The effects of the drugs on psychological well-being have been a topic of controversy, Whooley's team said.

Exactly how the drugs may confer protection against depression isn't known. Whooley said it is possible that statins' effects on the inner lining of blood vessels may play a role. The statins make the vessels less rigid, perhaps helping them adapt to the body's changing needs, she said.

It could also be that those who take statins are healthier overall than those who do not. The researchers tried to account for other lifestyle factors, such as exercise, she noted.

Whooley's study was not funded by drug companies. One co-author, Dr. Christian Otte, is on the speaker's board of AstraZeneca, Lundbeck and Servier, makers of statins or antidepressants.

Dr. Bryan Bruno, acting chair of psychiatry at Lenox Hill Hospital in New York City, reviewed the new study findings and said that the results may give heart patients motivation to take their statin medicines.

"You obviously can't confer any cause and effect" from the study, Bruno said. The researchers only found an association.

In consumer health information provided by the U.S. Food and Drug Administration, the agency said that some statin users report memory loss. The FDA also said that routine screening of liver enzymes is no longer needed while on statins. This is because the monitoring, once standard, has not been found effective in predicting the rare liver-injury problems. The agency also warns that some medicines interact with some statins in a way that increases the risk of muscle injury.